1. Field of the Invention
The present invention relates to a direct-injection compression self-ignition gasoline internal combustion engine having a fuel injector through which fuel is uninterruptedly (directly) injected into a combustion chamber of an engine cylinder and a piston whose compression action causes an air-mixture gasoline fuel within the combustion to be ignited by itself (self-ignition).
2. Description of the Related Art
Since, in a generally available gasoline internal combustion engine, when the air-mixture fuel is leaned to save a fuel consumption, a combustion due to a spark ignition through a spark plug and a flame propagation tends to become unstable, there is naturally a limit in the leaning of the air-mixture fuel. In addition, during a lean-burn combustion, a catalytic converter to purify an exhaust gas cannot exhibit its purification, particularly, a reduction action of NOx as high as the combustion which indicates a state of combustion in a combustion chamber at a time of a stoichiometric air-fuel mixture ratio.
To solve the above-described problem, a compression self-ignition gasoline internal combustion engine with a high compression ratio has been proposed which performs a self-ignition combustion caused by a compression action of a piston so as to achieve a lean combustion of the air-mixture fuel of gasoline and a low emission of harmful exhaust component as exemplified by a U.S. Pat. No. 5,535,716 issued on Jul. 16, 1996 (which corresponds to a Japanese Patent Application First Publication No. Heisei 7-332141).
In addition, a Japanese Patent Application First Publication No. Heisei 10-266878 published on Oct. 6, 1998 exemplifies another previously proposed compression self-ignition gasoline internal combustion engine.
In this Japanese Patent Application First Publication No. Heisei 10-266878, an interval of time is provided during which the combustion chamber is tightly closed between a valve-closure timing of an exhaust valve and a valve-open timing of an intake valve in a compression self-ignition drive region set from a low-engine-load region to an middle-engine-load region, a closure timing of the exhaust valve is retarded as the engine load is increased, a valve-open timing of the intake valve is set to be advanced so that the above-described tight closure time interval is gradually shortened. Furthermore, in the low-engine-load region and in a high-engine-load region, the valve-closure timing of the intake valve is made earlier (advanced) and, in the middle-engine-load region, the valve-closure timing thereof is made later (retarded).
Thus, a stable self-ignition drive under the engine load region from the low-engine-load region to the middle-engine-load and the high-engine-load regions becomes possible.
As the compression self-ignition gasoline internal combustion engine, an in-cylinder direct-ignition type gasoline internal combustion engine has previously been proposed. However, in this case, a mere setting of a fuel injection timing to a time point during a suction stroke of an engine cylinder to mix homogeneously air within the combustion chamber with fuel cannot achieve a favorable combustion stability and which, in turn, narrows a compression self-ignition combustion drive enabling range.
On the other hand, in the other previously proposed self-ignition gasoline engine disclosed in the above-identified Japanese Patent Application First Publication No. Heisei 10-266878, it is necessary to continuously vary the open-and-closure timings of the intake and exhaust valves with the increase in the engine load. A structure of such a continuously variable valve timing mechanism as described above is very complex and is difficult to be actually mounted in the engine. Hence, a reduction in engine reliability and a rise in cost in the manufacture and maintenance thereof cannot be avoided.
It is therefore an object of the present invention to provide a direct-injection compression self-ignition gasoline internal combustion engine which can extend the engine self-ignition combustion drive enabling range, achieving improvements in an intake-air charging efficiency and in a fuel saving and which can achieve a stable self-ignition combustion over a wide self-ignition combustion engine drive enable range with an improved self-ignitability without necessity of a complex continuously variable valve timing mechanism which would increase a manufacturing cost and maintenance cost and would reduce an engine reliability.
According to one aspect of the present invention, there is provided a compression self-ignition gasoline internal combustion engine, comprising: a fuel injector through which gasoline fuel is injected uninterruptedly within a combustion chamber of an engine cylinder; a piston of the engine cylinder whose compression action causes a mixture of air with gasoline fuel within the combustion chamber to be self-ignited; an intake valve whose open timing is set to a mid-way point through a suction stroke of the piston; an exhaust valve whose closure timing is set to a mid-way point through an exhaust stroke thereof; and a fuel injection controlling section that controls gasoline fuel injection timing and quantity per a combustion cycle injected through the fuel injector in such a manner as to set a first gasoline fuel injection to be carried out during a minus valve overlap interval during which both of the exhaust and intake valves are closed and as to set a second gasoline fuel injection to be carried out during at least one of the suction stroke and the subsequent compression stroke.
According to another aspect of the present invention, there is provided a compression self-ignition gasoline internal combustion engine, comprising: fuel injection means for directly injecting a gasoline fuel into a combustion chamber of each engine cylinder; piston means whose compression action causes a mixture of air with gasoline fuel within the combustion chamber to be self-ignited; intake valve means whose open timing is set to a mid-way point through a suction stroke of the piston means in a corresponding engine cylinder; exhaust valve means whose closure timing is set at a mid-way point of an exhaust stroke; fuel injection timing setting means for setting a timing of a first fuel injection carried out through the fuel injection means to a time point during a minus valve overlap interval during which both of intake and exhaust valves of each engine cylinder are closed and for setting that of a second fuel injection carried out through the fuel injection means to a time point during at least one of the suction stroke and the subsequent compression stroke, whereby the first and second fuel injections are carried out through the fuel injection means within the same combustion cycle.
According to a still another aspect of the present invention, there is provided a method applicable to a compression self-ignition gasoline internal combustion engine, comprising: providing a fuel injector through which gasoline fuel is injected uninterruptedly within a combustion chamber of an engine cylinder; providing a mixture of air and gasoline fuel within the combustion chamber to be self-ignited through a compression action of a piston of the engine cylinder; providing an intake valve whose open timing is set to a mid-way point through a suction stroke of the piston; providing an exhaust valve whose closure timing is set to a mid-way point through an exhaust stroke thereof; and controlling gasoline fuel injection timing and quantity per combustion cycle injected through the fuel injector in such a manner that a first gasoline fuel injection is set during a minus valve overlap time interval during which both of exhaust and intake valves are closed and a second gasoline fuel injection is set during at least one of the suction stroke and the subsequent compression stroke.
This summary of the invention does not necessarily describe all necessary features so that the invention may also be a sub-combination of these described features.